updated 05:17 am EDT, Sun May 19, 2013

How do the US and international versions of the Galaxy S4 stack up?

We have already published our full review of the Galaxy S4 for the US, which ships with a Qualcomm Snapdragon 600 quad-core processor. In some international markets, the Galaxy S4 ships with Samsung's own Exynos 5 Octa, an eight-core chip that uses ARM's big.LITTLE architecture. We have been using one for the past week, putting it through its paces, although our focus here is to see whether US customers are missing out on any performance.

Samsung says that the two chips are roughly equivalent in performance, although in reality, there are some differences between the two. The quad-core Snapdragon 600 in the US version of the Galaxy S4 is the latest iteration of Qualcomm's Krait mobile architecture and is clocked at 1.9GHz. It is built on a 28nm process and is at least 40 percent faster than its 2012 performance flagship, the Snapdragon S4 Pro. It is also paired with the latest version of the Adreno 320 GPU, clocked at 500MHz.

The Samsung Exynos 5 Octa, is fabricated using ARM's big.LITTLE architecture integrating four performance Cortex-A15 cores (1.6GHz) with four low power Cortex-A7 cores (1.2GHz) on Samsung's 28nm HKMG process. Although the chip technically has eight-cores, it is for all intents and purposes a quad-core chip as the eight-cores do not function in unison. It uses an Imagination Technologies PowerVR SGX544MP3 with a triple-core GPU clocked at 533MHsz. As a side-note, it is interesting to note that Imagination Technologies is 10-percent owned by Apple and Samsung actually switched from ARM's Mali mobile GPUs to PowerVR for this generation of its mobile processors.

In terms of raw performance, both chips are among the fastest mobile processors in any currently shipping device. However, the real-world performance of the chips using Samsung's TouchWiz implementation of Android is far from optimal. As a number of observers have noticed with the US version of the Galaxy S4, even though it runs the latest version of Android 4.2.2 'Jelly Bean,' it is prone to being "janky." This means that when apps launch, they can stutter, while when scrolling through web pages, it can pause briefly. We also noticed the home screen clock and weather widget would sometimes momentarily when returning to the home screen after being in an app.

This is apparent on both the Snapdragon 600-equipped Galaxy S4's as well as the Exynos-equipped versions. Clearly the speed of the processors is not an issue, so we can only put this down to the amount of bloatware on the Galaxy S4 as well as the number of beta 'features' like eye scrolling. It seems that in adding all the additional functionality to TouchWiz, which makes for great marketing opportunities, the stability of the OS has suffered somewhat. However, we fully expect Samsung to issue patches to address this in time.

In objective tests, however, the Galaxy S4 with the Exynos 5 Octa shines. Even though it is clocked 300MHz slower than the Qualcomm Snapdragon 600, it produces a Geekbench 2 score higher than the US model. The Exynos 5 produces a score of 3533 against the score of 3238 produced by the Snapdragon 600. The Galaxy S III produces a score of 1764, showing that the in either variant, the Galaxy S4 is much faster. However, it is also clear that the Exynos 5 has a performance edge over the Snapdragon 600 in raw processing performance.

When it comes to the graphics performance of the Adreno 320 against the PowerVR SGX544MP3, the two GPUs perform much more closely. However, in this case, the Adreno 320 has a slight edge over the PowerVR. The Futuremark 3DMark reveals that the Galaxy S4 with Adreno graphics produces a score of 6651, while the Galaxy S4 with PowerVR scores 6545. Both chips produce a prodigious 51 gigaflops of performance, so in real terms little really separates them.

One of the surprise, but welcome, announcements at Google I/O last week was the news that it will start selling a Samsung Galaxy S4 with stock Android from June 26. Although not a Nexus device, it will also benefit from timely updates to its OS, just like Nexus devices. While it will produce very similar performance to the Galaxy S4 in either Snapdragon or Exynos trim, it is quite likely that from the perspective of real-world performance, this will be the version of the Galaxy S4 to get. However, you will be sacrificing numerous software features that are only available in the Samsung TouchWiz version of the Galaxy S4.

It will be very interesting to see which model consumers veer towards. Our preference, thus far, has been to use Google's Nexus range for getting the optimal Android experience. As much as we like the HTC One, we would still opt for a stock Android version of that device if HTC ever released one. Highlighting this is the fact that, even though the quad-core Snapdragon S4 Pro in the LG Nexus 4 is outgunned by the newer chips in the Galaxy S4, its Android experience much more seamless and stutter-free that the Galaxy S4 as it currently stands.

The Galaxy S4 is a very powerful smartphone in either Snapdragon 600 or Exynos 5 variants. If Samsung can get on top of the minor, but annoying, software glitches in TouchWiz through a future update, most users will probably not notice any performance difference in using either version of the device. Power users, however, will probably want for every single extra clock cycle of CPU power they can get. In that case, the Exynos 5 version is probably the one to get if you are prepared to pick one up from an importer and hack your choice of ROM on to the device.

The stock rom on the Exynos 5 version is just fine, why would you change? The phone is lightning fast and the battery lasts (relatively) forever... and the hardware links you would lose would be foolish (air gestures, IR blaster, etc).